1. Field of the Invention
The present invention relates to an antenna selection system and method, and a radio communication apparatus using the same system, and more particularly to an antenna selection system for use in a radio communication apparatus of W-CDMA method having a plurality of antennas.
2. Description of the Related Art
In the mobile communication field, a mobile unit is required to comprise two antennas. One of the reasons why the above feature is required is that when the antenna is hidden by a hand carrying the mobile unit, the antenna characteristics are degraded. Also, since the receiving condition is changed due to movement of the user, it is required that a selection operation between two antennas is appropriately performed.
However, in the case where one of two antennas is selected, there is a problem that when the antenna is changed by a switch or the like during communication, data loss or retransmission occurs or receive is disabled at the time of switching, because a multi-path situation of each antenna is different.
There is a technique for performing the antenna selection operation during transmission interruption by making a temporary transmission interruption request to a base station (refer to Japanese Unexamined Patent Publication No. 03-293825). Also, there is another technique for performing the antenna selection operation when the received signal quality is degraded during communication using one of two antennas (refer to Japanese Unexamined Patent Publication No. 2001-156752).
However, in the technique of Japanese Unexamined Patent Publication No. 03-293825, a phenomenon of communication interruption positively occurs when the transmission interruption request is made. Also, the techniques of Japanese Unexamined Patent Publication No. 03-293825 and Japanese Unexamined Patent Publication No. 2001-156752 do not provide the solution when a signal is interrupted during communication and have a problem that the downlink data loss occurs.